It is known that enamines or imines can be hydrolyzed quantitatively by, for example, dilute acids to form aldehydes or ketones, which aldehydes or ketones can be used to synthesize terpene compounds which are useful as, for example, flavor components or drugs such as vitamins. Thus, they are very important intermediates.
Known methods for the preparation of enamines or imines by the isomerization of allylamine derivatives include a method in which strong bases are used as catalysts (H. Sauer et al., Chem. Ber., 102, 1917 (1969)), a method in which metal oxides are used as catalysts (Tanable et al., Chem. Lett., 1465 (1977)), a method in which cobalt complexes are used as catalysts (Japanese Patent Application (OPI) Nos. 5906/79 and 5907/79 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application")), and a method in which palladium complexes are used as catalysts (Japanese Patent Application (OPI) No. 162730/80).
As a result of extensive investigations on catalysts for use in such isomerization, it has been found that rhodium complexes permit isomerization of allylamine derivatives into enamines or imines in high yield.